...............
Catching up... Mr. Marsden coached me to clear my cookies / cache .. this worked well, and the problem has not returned...

 

I also got this error while trying to move a thread yesterday. I solved it not by refreshing the page, but by closing the tab altogether and starting the operation fresh.

Tell us if that works for you.

Also, please see my other post in that other thread.

 

Hello,

I think that the problems are cloudflare related.
I have notified jrap about the issue.

Bertus